1. Field of the Invention
The present invention relates to an elastic wave device that includes a piezoelectric substrate and a plurality of interdigital transducer (IDT) electrodes that are provided on the piezoelectric substrate. More specifically, the present invention relates to an elastic wave device that includes a plurality of IDT electrodes that are sealed with a support layer and a cover member.
2. Description of the Related Art
In the related art, various elastic wave devices that are called wafer-level packages (WLP) have been proposed. International Publication No. WO 2009/116222, which will be described below, discloses an example of this type of elastic wave device. A plurality of surface acoustic wave elements are formed on a single piezoelectric substrate. Each of the surface acoustic wave elements includes an IDT electrode in at least a portion of the surface acoustic wave element. In International Publication No. WO 2009/116222, in order to seal the surface acoustic wave elements, a support layer is formed on the piezoelectric substrate in such a manner as to surround the surface acoustic wave elements. A cover member is joined to the support layer. As a result, hollow portions in which the surface acoustic wave elements are present are formed.
In the elastic wave device described in the above-described International Publication No. WO 2009/116222, the cover member is stacked on and joined to the support layer. A void may sometimes be generated in a joint portion between the support layer and the cover member. Thus, the void may sometimes allow communication between the hollow portion and the outside, and as a result, the airtightness of the hollow portion may sometimes be reduced resulting in a leak defect.